Binder for laminated mica products



I06. courosulous,

COATING R PLASTIC.

Patented 2, 1929.

UNITED STATES EXammef PATENT OFFICE.

TORAZO OKURI, OF TOKYO, JAPAN.

BINDER FOR LAMINATED MICA. PRODUCTS.

No Drawing. Application filed November 9, 1926. Serial No. 147,395, and in Japan August 5, 1926.

M invention relates to insulating and noneat conducting mica plates, for-use in electric heaters, more especially plates built up of a plurality of pieces of mica united together by an insulating inorganic paste composed of inorganic salts (fire-clay, bo rate, silicate, magnesium chlorate, and caustic soda). The object of the invention is to obtain, inexpensively, mica plates which have good insulating and non-heat conducting properties, and which can be manufactured in numerous shapes, sizes, and thicknesses like natural mica plates and to this end, I have invented an adhesive by which the mica material may be united to give a strong mass having excellent insulating properties.

Hitherto, mica plates used in electric heaters have been mainly natural mica plates, but they are naturally restricted as to their shapes and sizes. Moreover, natural ones can not be said to be perfect in respect to their proof against heat, for it is generally experienced that when heated up to a temperature of 800 C. or so, they become cracked and fail, and accordin ly their insulating power is lessened. lVfy invention, however, is to obviate these defects, and its essential feature is to take mica pieces of various sizes and shapes, and solidify them with a special insulating inorganic paste. The paste used must be an insulating and adhesive substance and is produced by treating several kinds of inorganic salts, that is, fire cla borate, silicate, magnesium chlorate, an caustic soda.

The following is an example illustrating one method of carrying this invention into practice Take fire clay, potassium boratemr sodium borate, potassium silicate or sodium silicate respectively in a quantity of water, hfiat the mlxtlll, up 0 a temperature of a out 15020 0 Y vwit agitation. Put the milky fitjmed thereby into an autoclave with the proper quantities of magnesium chlorate and caustic soda, and put under heat and pressure till a sticky inorganic paste is obtained. In this case, these salts should be pure and anhydrous, and

the proportion of their quantities is advantageously as follows Parts. Fire clay 1-3 Potassium borate or sodium borate 2030 otassium s1 ica e or sodium silicate-" 2-5 Magnesium chlorate 0.5-1 Caustic soda 0.5-1

Then, apply the insulating inor anic paste thus obtained, with brushes or t e like, to mica flakes or pieces of about one mil thickhess, paste them together to the required shape and thickness, and under a little heat and pressure mold them in the shape OI 5" hardly display such a strong proof against heat; but when the s ecial inorganic paste of my invention solid i fies mica plates, they become denser, as they are heated, than at usual temperature. Therefore, the original nature of mica is protected, and accordingly, can display such proof against heat as above described. Furthermore, as the mica used as material can be in the form of flakes or fine pieces, it is much cheaper as compared with natural mica plates, and besides, it is not restricted as to its sizes and thicknesses.

\Vhile the heating coil which touches with mica plate is protected by the non-heat conducting mica plate, it has the great advantage of lengthening the life of resistance wire.

Having now particularly described and as certained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. In a laminated mica product, a binder for the mica laminae comprising the reaction product of heating under pressure an aqueous mixture comprising fire clay, an alan alkali metal silicate, 2-5 parts, magnesium chlorate, 0.5-1 parts and caustic soda, 0.5-1 parts.

In testimony whereof I have afiixed my signature.

TORAZO OKURI. 

